At 91, Elaine LaLanne is following in her husband's footsteps. She swims, lifts weights and even does push-ups to stay strong.

"A lot of people say they got a bad back -- well, work around your infirmities. Keep moving. Simple as that," said LaLanne.

It's a great way to look at life, and she isn't alone. Ultra marathoner Shannon Farar-Griefer shares the attitude.

"I'm 56 years old and I have MS so it's been really helpful with my balance as well and strengthening my muscles," said Farar-Greifer.

Farar-Griefer recently bought the Stealth. It's a core board of sorts that makes a game out of working your abs.

"Planks are so boring and so challenging so it's mental and physical torture together. Stealth is playing a fun game and you don't realize you're doing a plank," said fitness pro Eric the Trainer.

The beauty of the product is that it works your core, but more importantly, you get other body parts like your upper back, your shoulders and your arms. It's a game-changer.

Right now, there are three games to play while in plank position. You can use your body to guide the track ball to certain points on the screen, which takes muscle control and concentration. Your core gets a workout in about two minutes time.

"It's a great tool for posture. It's a great tool for strength. It's a great tool for older people to connect with their cores again," said Eric.

Eric was a consultant on creating this core tool that just came off a Kickstarter fund.

You can download the app for free, but currently the Stealth is $299, so your best bet may be to give it a test-drive a gym like Eric's.